List.pushFirst
pushFirst($item) -> self
Description
This function is like push, but it adds an item to the beginning of a List.
This function is the opposite of popFirst.
$letters = ['a', 'b']
$letters.pushFirst('X')
//= ['X', 'a', 'b']
$letters.popFirst()
//= 'X'
print($letters)
//= ['a', 'b']